[in progress] Squares

Hello,
this is my 1st playable game, it's a 2D platformer but also it include a kind of a "level editor" (not sure if i can call that a level editor )
i build it with Java using the Lwjgl library, i only tested the game on windows so if you're using another OS please excuse me if you face an error or if the game didn't work

the game for now contain only 4 levels , there is no death or losing, you just have to go to the target point.
you can also edit or recreate all the 4 levels and save them as well but please finish them first

Current Goals :
*optimize the collision systemwhen you play the game you'll notice the trouble with the collision (specially with the ground) if anyone has face this kind of trouble before and know a "theory" for fixing it, i will be very grateful for your help

*optimize the file systemmaking the player choose the name of the level before saving it, and also allow them to choose what level to loads

*create a menu

PS :
"F" suppose to run the game in full screen, it works for me, but someone else test it and she said that it doesn't work for her, please tell me if it works for you